London (CNN) Brexit officially began Wednesday after UK Prime Minister Theresa May triggered Article 50 , kicking off Britain's withdrawal from the European Union and the painstaking legislative to-do list that comes with it.

One of the next key steps will come when May's government introduces the Great Repeal Bill.

The bill is designed to put an end to the EU's legal jurisdiction over the UK. But first it will transpose all current EU laws into the UK statute books "to ensure the maximum stability on exit," the government says.

Parliament will then begin the daunting task of deciding which EU laws to keep and which to scrap, essentially untangling four decades of EU rules now enshrined in UK legislation.

There are nearly 20,000 EU legislative acts in force that make up a mind-boggling set of rules dictating everything from how much clean energy a country should use to the acceptable curvature of a grocery store banana.

So where will the government begin? Here's a list of just 50 things the UK will need to work out as it sets sail on its own.

The big questions

1. A new immigration system

Immigration was a key issue in the Brexit debate. After the UK withdraws from the union, a system to allow its nationals to visit, work, study and live in the EU -- and vice versa -- must be hammered out.

The UK is currently part of the European Single Market, which allows goods, services and people to move freely through member states. EU citizens have the right to travel and seek work in other EU countries. Roughly 1.2 million Brits were settled in the EU in 2015, and around 3.2 million EU nationals were living in the UK, according to government statistics

But as May has made clear, the UK will no longer be part of the single market , so this free movement will come to an end after Brexit.

The idea of a points-based system like Australia's has been floated, with the aim of attracting immigrants with certain skills to fill gaps in the economy.







2. Asylum seekers and refugees

But that law will no longer apply after Brexit, so those countries won't be obliged to receive asylum seekers whom the UK wants to send back. If the UK wants to preserve the principle of Dublin III, the government must negotiate separate bilateral arrangements with each individual country.







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3. A trade deal with the EU

One of the most contentious points of the Brexit debate was the UK's trade relations with the EU. A new trade deal is expected to be one of the most difficult and important parts of the negotiations.

The UK intends to leave the EU's single market and may also leave the EU customs union, through which Britain enjoys tariff-free trade. If no trade deal is agreed upon, the UK would have to trade with the EU under World Trade Organization rules , which could lead to new tariffs and regulations.







4. Trade deals with everyone else

Post-Brexit doors are opening for the UK to strike new trade deals with non-EU countries like the US, China, Brazil, Australia and Canada. As a member of the EU -- which negotiates trade deals as a bloc -- this would not have been possible.







5. Security vs. privacy

The UK government has proved nosier than most of its EU counterparts -- last year, Parliament passed the Investigatory Powers Act , better known as the "Snooper's Charter," which gives UK law enforcement agencies unprecedented access to personal data and requires telecommunications companies to store web-browsing histories for a year.

But the EU has strict data protection laws -- including one directive, for example, that says EU countries must guarantee that information is stored or accessed only if the user has been informed and been given the right of refusal.

The EU in December ruled that parts of the "Snooper's Charter" were unlawful . When the UK leaves the EU however, the judgment will be rendered invalid.







6. Law enforcement

The peculiar and pedantic

7. Working out what jam is

In 2010, an EU directive was passed stating that jams must consist of 60% sugar and come from a list of approved fruits in order to be classified as jam. The directive alarmed many small business owners already marketing their product as jam, who thought they would have to either change their labels or sugar content due to the regulation.

In 2013, Michelle "Clippy" McKenna, a British apple preserve maker, argued that her product was a jam even though it didn't cross the sugar threshold -- but it turned out that there was a clause in the EU rule allowing for exemptions. It was just that the UK had not included this clause into its own law . The government has kept a lid on its plans to amend any food directives for now, although Brexit would allow the UK to can the jam rule altogether should it wish to.







8. Pig semen

Want to import pig semen into the EU? Farmers seeking to improve the quality of their pork must obtain pig semen from an authorized collection center and make sure it comes with an animal health certificate, according to another EU directive . It's not clear how the future of the swine gene pool will be affected by Brexit yet -- but it's surely on the minds of the farmers overseeing the 10,000 pig farms in the UK







9. Bright lights

Could traditional incandescent light bulbs make a return to high street shelves in the UK? The UK mostly phased out incandescent bulbs following an EU directive favoring more energy efficient options in 2009. But the regulation only applied to domestic use , and to this day the traditional light bulbs are commercially available in the UK. It's possible Britain could bring back the bright lights after Brexit.







10. Bendy bananas

The EU rules on bananas have long been the subject of mockery. According to the 1994 regulation , bananas must be "free from malformation or abnormal curvature," be more than 14 centimeters in length and come in bunches of at least four. Other parts of the regulation say the fruit must be free from pests and mostly free of bruises. Bananas might be bendier after Brexit -- but could they be less appetizing too?







11. Footwear labeling

Look at the label on your shoes. If you bought it in the EU, you'll find information about the materials used to make them. EU law specifies that shoe labels must be embossed on the footwear or attached by an adhesive label, fastener or string. Shopping for shoes after Brexit could be a much more confusing affair if the UK doesn't find its footing with a new bill.







12. Move your horses

If you want to move a horse within the EU, strict rules apply . The animal must show no sign of disease in the 48 hours prior to traveling and must have had no contact with horses that have an infectious disease in the previous 15 days. But countries outside the EU face even tougher rules, including additional inspections by experts from EU countries and the European Commission. A post-Brexit UK may need to negotiate a separate arrangement to avoid these stricter regulations.







13. The future of football

The rules around sporting transfers are likely to change when Britain leaves the EU -- and impact one of the world's most watched leagues

That means once Britain's demarcation from the EU is finally drawn, footballers looking to ply their trade in the English Premier League -- or in Scotland, Wales and Northern Ireland -- are likely to be subject to a tougher set of rules that govern transfers from outside the region.

The English Football Association in 2015 tightened the rules for non-EU players joining English teams in an effort to give indigenous players more chance.

So non-EU players had to have made a minimum number of international appearances for a top-50 country over the previous two years (the higher the ranking, the fewer the number of matches necessary).

Spanish superstar footballers, for example, may have to get the same work permits as Brazilians to play in post-Brexit England.







14. Safety at work

EU laws on health and safety at work are often mocked for being excessive. Employers must make sure workers have information about the weight and weight distribution of a load before handling it, and they must organize workstations to make handling as safe as possible. The directive warns of increased risks if the floor is uneven, the load is unwieldy or the worker is wearing unsuitable clothing. Without this law, or a similar replacement, is UK workplace safety in jeopardy?







15. The future of coloring in

The EU is currently attempting to introduce new measures limiting the amount of lead allowed in toys and items that may be chewed on by children. Some British media characterized the proposal as little more than bureaucrats in Brussels clamping down on coloring pencils and crayons.

According to the European Chemicals Agency, the average lead content in the blood of European children is up to four times higher than recommended . EU toy safety regulations are some of the toughest in the world . It is unclear if the UK will stick to these rules after Brexit.







16. Noisy vehicles

An EU regulation aims to cut down on noise pollution by ensuring new cars are a little quieter than before. In three stages, it will ban new four-wheel passenger vehicles that are louder than 77 decibels by 2026, and vehicles carrying goods will be limited to 79 decibels. It also requires electric and hybrid cars to make artificial engine noises to avoid accidents, especially involving pedestrians. The chances of Britain being flooded with annoyingly noisy vehicles after Brexit seems unlikely, but the country may not stick to such stringent rules.







17. Trade in torture instruments

EU member nations are banned from importing items that have no practical use other than carrying out capital punishment, torture or inhuman or degrading treatment . Among them are electric chairs and shock belts, shackles, gallows, guillotines and pepper spray. Revisiting this law could make for some interesting deliberations in UK Parliament.

The nitty gritty

18. Brits abroad

At the moment, UK nationals can turn up to an EU country, flash their passports and be granted freedom of movement within the union. But once the country pulls out of the EU, this privilege could come to an end.

The government will need to negotiate a deal for its citizens and will likely try to retain visa-free travel. But the European Commission may have other ideas -- it currently has a proposal on that table for a visa waiver system , much like the scheme in the United States, to tighten screening of all non-EU members entering the EU. This would involve applying online for a visa ahead of time and paying a small fee to be given access to the zone.







19. Roaming charges

EU citizens pay relatively low roaming fees for phone calls and data usage within the EU. And the union is aiming to abolish roaming charges altogether by June this year

As outsiders, telecommunications companies will not be obliged to offer the same low rates to British travelers, and these rates may come down to what kind of deal the government strikes with the EU.







20. Cost of air travel

Air travel between EU countries has become much more affordable since the EU removed several competition barriers , allowing budget airlines to flourish. But after Brexit, UK airlines such as EasyJet won't be able to take advantage of these benefits and will need to make new agreements to operate in EU airspace, according to the Chief Executive of the Civil Aviation Authority. The impact this could have on prices is unclear.







21. Air passenger rights

If you're an EU citizen and your flight is canceled or delayed, or if you're denied boarding against your will, you are entitled to various forms of compensation under EU law. Even if you're simply seated in a class lower than you paid for, you can claim up to 75% of the price of the ticket. After Brexit, UK citizens will no longer have these rights.







22. The 48-hour work week







23. Carers' rights

landmark 2008 European Court of Justice decision ruled that non-disabled employees are protected by law if discriminated against on the basis of their association or care for a disabled person. For example, if an employer discriminated against a parent caring for a disabled child, the parent could claim for discrimination. After Brexit, the UK government will be free to decide on the future of carers' rights in the workplace.







24. Equal pay for agency workers

The EU has also obliged employers to pay temporary agency workers at the same rate as permanent employees. The government may choose to revisit this rule, which Open Europe says costs the economy a further £2.1 billion ($2.6 billion) a year







25. Part-time workers' pension

Rulings by the European Court of Justice obliged the UK to enroll part-time workers in employer pension schemes -- not doing so was seen as discrimination against women , who work part-time roles in higher numbers. It is unclear whether the government will reconsider this rule.







26. Annual leave

Under EU law, if you get sick while on annual leave, you can retake that leave at a later date and even carry it over into the following year. According to the Local Government Association , this conflicts with UK law, which doesn't allow employees to carry over leave from one year to the next. This conflict may mean that this particular EU regulation is scrapped after Brexit.







27. Gender equality

Under its Strategic Gender Equality plan , the EU allocated 6.17 billion euros ($6.7 billion) between 2014 and 2020 to reach certain targets, such as reducing the gender pay gap, preventing and combating violence against women and getting more women involved in science, technology, engineering and mathematics. The UK government will need to decide how to fill this funding gap, post-Brexit.

In his 2017 spring budget speech, Chancellor of the Exchequer Philip Hammond pledged to commit £20 million ($25 million) of government funding to support a nationwide campaign to stop violence against women and girls. Hammond also reinstated the controversial "tampon tax," a 5% tax placed on the sanitary item, which will be used to deliver an additional £12 million ($15 million) in support of women's charities nationwide, according to Hammond.







28. Maternity leave







29. Erasmus

UK university students currently have access to Erasmus , an EU student exchange program that allows them to study in another Erasmus country for three to 12 months. Nearly half of all UK students who travel to study elsewhere for a short period do so through this scheme. Access to Erasmus will no longer be automatic and will have to be renegotiated.

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30. Recognition of qualifications

EU citizens who get a professional qualification in one EU country may work in another safe in the knowledge that their skill -- whether it be accounting, teaching, beekeeping or wine-tasting -- will be recognized.

It's fairly simple for UK citizens to find work or training elsewhere in the EU by using the European Qualifications Framework and the Europass to list their skills and qualifications. These standardized documents help universities and employers to compare applicants from countries across the EU. Once Britain has left the EU, UK citizens may not be able to access these tools and countries may decide not to recognize each other's qualifications unconditionally.







31. Horizon 2020

A number of UK universities, including Edinburgh, Manchester, Oxford and Cambridge, have received millions of euros in funding through Horizon 2020 , an EU program that promotes research into topics as diverse as health and well-being, green transport, outer space and future technologies.

According to the "white paper" on Brexit, the government "will work with the European Commission to ensure payment" when funds are awarded in research programs including Horizon 2020 . It promised to guarantee such grants, even if projects continue after the UK leaves the EU. The role of UK universities in future EU-led research programs remains unclear, however.







32. CO2 Emissions

The UK is part of the EU Emissions Trading System , the cornerstone of the EU's climate change policy and the world's first and biggest carbon market. Under the ETS, a cap is set on the total amount of certain greenhouse gases that can be emitted, and is reduced over time so that total emissions fall. The system is now in its third phase -- where a single, EU-wide cap on emissions applies in place of the previous system of national caps. If the UK leaves the ETS, the EU-wide cap will need to be adjusted and legislation introduced to keep the UK's CO2 emissions in check.







33. Keeping beaches clean







34. The air we breathe







35. The fate of wild birds







36. Animal welfare

Farm animals kept in the EU must be fed a wholesome diet, have enough space to move around and be treated immediately if they're sick or injured, according to one directive . There are around 40 other pieces of EU legislation that also deal with animal welfare , according to the RSPCA. As the government has made clear it won't remain in the EU's single market, Parliament will have to decide which regulations to keep and which to drop.







37. Save the bees

Two years later the UK granted farmers an emergency authorization to use them on oilseed rape seeds. The UK expressed doubts about the effectiveness of the rules and could alter or drop them after Brexit.







38. Getting treatment







39. Dealing with pandemics

The EU has an early warning and response system for potential public health threats, such as the SARS epidemic in 2003. Countries can easily share information, pool resources for lab investigations and work together to develop new strategies for future threats. After Brexit, the UK won't be part of this system and will have to develop other ways of coordinating with EU countries.

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40. EU health program

Through the EU health program , launched in 2014, EU countries work closely together to combat unhealthy behaviors, such as smoking and drug and alcohol abuse, by sharing information and good practices. Projects with these goals can receive up to 80% of their funding from the EU. The UK may still be eligible to be part of the program after Brexit but membership is not guaranteed.







41. Disease prevention and control

The European Centre for Disease Prevention and Control works to identify and combat threats to human health from infectious diseases such as influenza, waterborne diseases and HIV. It makes it easier for organizations across the EU to share information and expertise.

According to a report by the Royal College of Physicians , programs managed by the ECDC "could not be effectively fulfilled by national governments independently." After Brexit, the UK would be excluded from the ECDC and would need to negotiate a special arrangement to remain a member.







42. Medicine

Under mutual recognition licensing , any medical product licensed in the UK can be distributed throughout the EU.

At a recent hearing , Health Secretary Jeremy Hunt confirmed that after Brexit the UK won't be part of the European Medicines Agency, the body responsible for authorizing new medicines, and instead hopes to negotiate its own form of mutual recognition agreement with the EU.







43. Road safety

Vehicle and road safety is covered by a long list of EU laws. EU regulations set out safety standards for all kinds of vehicles and even specify the type of crash protection systems required for vehicles in order to reduce the number and severity of injuries to pedestrians. After Brexit, the UK will be responsible for introducing national road and vehicle safety laws to protect its citizens.







44. 'Passporting' for the finance industry

A gripe for the finance industry during the Brexit debate was the possible loss of "passporting" -- the right for UK businesses to provide financial services anywhere in the EU and the wider European Economic Area while being based in the UK and regulated by UK authorities.

In the Brexit negotiations, the government could try to retain this right as part of a new agreement with the EU.







45. Firearms

EU law sets out strict regulations on who can own a firearm and buy ammunition. Among other things, the law requires EU states to keep a database of registered firearms and carry out regular checks on license holders. The law was also designed to make it easier for countries to share information about firearms and their movements around the EU. After Brexit, the UK could decide to loosen or tighten these regulations in its own laws.







46. Rules on tobacco

The EU has strict rules on how cigarettes and other tobacco products can be manufactured, marketed and sold. EU law is behind the large health warnings on cigarette packets. It will soon prevent extra flavors such as fruit or menthol being added to tobacco products that could encourage people, especially young people, to start smoking. Although the UK has strict tobacco laws of its own, the government will need to clarify where it stands on EU regulations, such as the ban on menthol cigarettes, which are currently available widely.







47. Irish dairy

For Irish dairy farmers whose land straddles the border between Northern Ireland and the Republic of Ireland, Brexit could have significant implications. If a "hard border" is imposed, new import and export charges could be introduced This could mean big costs: 30% of total of Irish dairy exports go to the UK

Farmers who have cows and a bottling plant on one side of the border, but with the milking equipment on the other side, could be hit with these import/export taxes if a hard border is introduced. As of now, it's not clear what will happen to the common travel area that exists between Northern Ireland, which will remain part of the UK, and the Republic of Ireland, which will stay in the EU. The British government said that its aim is "to have as seamless and frictionless a border as possible" in a 77-page "white paper."







48. The French border

In 2003, the French and UK governments signed the Le Touquet accord, which allows the UK to check passports in France and effectively situates the border on French soil. The agreement has nothing to do with EU law but last March the then French Economy Minister Emmanuel Macron suggested Le Touquet could end if Britain voted to leave the EU.

Macron also warned that migration to Britain would increase if it left the EU , including from those who had camped out for months at a camp in the French city of Calais.

Macron is now a frontrunner in the presidential election, and he hasn't forgotten his pledge. At a campaign rally in London in February, he suggested he would try to partly renegotiate the agreement . Softer language perhaps, but the possibility of a change to border arrangements remains.







49. Keep broadband affordable

The EU has put in place a set of rules that are intended to help keep broadband costs down. They oblige governments to clear any legal obstacles that may hold back network operators from giving telecoms operators access to their physical infrastructure on reasonable terms and conditions, including price.







50. New passports