(Reuters) - Grappling with a ballooning number of mostly Central American families seeking asylum at the U.S.-Mexico border, President Donald Trump has suggested increasingly bold steps to limit protections for this group and stem their entry into the United States.

A general view shows a temporary facility for processing migrants requesting asylum, at the U.S. Border Patrol headquarters in El Paso, Texas, U.S. April 29, 2019. REUTERS/Jose Luis Gonzalez

Yet many of his administration’s ideas have been hindered by legal, practical and political obstacles.

Increasingly frustrated, Trump on Monday issued a presidential memorandum directing officials to make it harder for asylum seekers to apply for work permits and to charge them application fees - drawing immediate fire from the United Nations.

The proposals face a potentially lengthy regulatory review and once rules are issued they may be subject to legal challenges. Many asylum protections are codified in U.S. and international law.

Meanwhile, the flow of migrants continues to swell. In March, the monthly number of people apprehended and deemed inadmissable at the U.S.-Mexico border surged to more than 100,000, the highest level in more than a decade.

Migration is largely driven by poverty, corruption, crime and other factors in Honduras, Guatemala and El Salvador where the bulk of people are coming from.

Some examples of administration proposals or policies that have run or may run into trouble:

INCREASE BARRIERS FOR ASYLUM APPLICATIONS

Monday’s presidential memorandum directed the Justice Department and Department of Homeland Security to introduce new regulations tightening asylum policy within 90 days.

In addition to setting a fee for asylum applications, which are currently free to file, the memo ordered officials to issue rules to ensure claims are adjudicated in immigration court within six months. That provision already exists in U.S. law but has been hampered because of a crushing backlog of more than 800,000 immigration court cases.

The president of the immigration judges’ union said the goal is not feasible without a significant increase in resources for the courts.

DETAIN ASYLUM SEEKERS INDEFINITELY

U.S. Attorney General William Barr recently issued a ruling that allows asylum seekers who cross the border illegally to be held without bond as they challenge their deportation – a decision affecting perhaps tens of thousands of migrants.. It was the latest move by top justice officials seeking to reshape legal precedent in the country’s U.S. immigration courts.

Rights groups have already threatened to sue over the measure - which goes into effect in 90 days - and as a practical matter, additional detention space would be needed, requiring funding from Congress. Until that happens, many migrants are likely to continue to be released with an order to appear in court.

BAR GANG AND DOMESTIC VIOLENCE VICTIMS

Before leaving office, U.S. Attorney General Jeff Sessions intervened in an immigration case to overturn asylum protections for a domestic abuse survivor. His opinion sought to narrow protections for migrants fleeing sexual and gang violence perpetrated by private actors.

In December, however, a Washington D.C. District court judge struck down the policy change and ordered the government to bring back six deported asylum seekers who sued the administration seeking reconsideration.

PREVENT ASYLUM BETWEEN PORTS OF ENTRY

In November, Trump issued an order that would prevent migrants who cross between official U.S. ports of entry from applying for asylum. The administration has implemented a policy of “metering” how many applications can be processed at legal border crossings. Advocates say that has pushed more large groups into the hands of smugglers who drop them off at illegal entry points with instructions to turn themselves into border agents.

Migrant rights groups rushed to court to block the policy and a San Francisco-based federal judge temporarily halted it the same month it was issued. [L2N1XU14R] The U.S. Supreme Court declined to immediately overturn that ruling.

MAKE ASYLUM SEEKERS WAIT IN MEXICO

One of the boldest proposals by the Trump administration has been to tap a little-used clause in immigration law to send hundreds of asylum seekers back to often dangerous border towns in Mexico to wait months - or potentially years - for their cases to be resolved in U.S. courts.

Local Mexican officials say their towns already are overwhelmed with migrants who have nowhere to live and few job prospects, while immigration advocates say those who are stuck in Mexico often have trouble finding lawyers and receiving proper notice for their U.S. hearings.

A federal judge ordered a halt to the policy but an appellate court said it could continue while the administration appeals. Since the policy went into effect in late January through April 22, nearly 2,000 Central Americans have been returned to Mexico to await their hearings, according to Mexican immigration officials. Many remain there with their status in limbo.