Is it OK for the boss to make employees mix business with politics?

Some workers and their bosses might be asking that question after employees at a Royal Dutch Shell construction site in Pennsylvania were told that while they didn't have to show up to hear President Donald Trump speak last week, not attending could result in their not being paid .

The scenario was legal, some experts say, though not without controversy.

Trump’s speech took place at a construction site where Shell is building a petrochemical plant.

Employees were given two options: to not go to work that day, which would mean an excused absence, or to come to work and get paid, says Shell spokesman Ray Fisher. Training sessions for employees were held in the morning, from 7 a.m. to 10 a.m., but after that, the site was closed,

“As with most hourly positions, they would not be paid for the hours they did not work,’’ Fisher said in an email. “As a result, they would not be eligible for the maximum overtime available that week.’’

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The two choices were given to workers because “it was assumed some would not want to attend,’’ Fisher said, adding that the same options are offered to employees “regardless of who the guest speaker is.’’

But the situation raised the ire of one union leader, whose organization was not involved in the event.

“In a democracy, people should have the right to their own political views, but Trump and Shell embarked on a slippery ethical slope by making a paycheck conditional on attending a glorified campaign rally,'' Randi Weingarten, president of the American Federation of Teachers union, said in an email.

Shell wasn't worried that it would look like it was compelling or coercing workers to attend what could be viewed as a political event, Fisher said.

“This was treated as a training day with a guest speaker who happened to be the president,’’ he said. “We do these several times a year with various speakers. The morning session included safety training and other activities. For those who chose to attend, our guidance was to show respect for the speaker as we would for any guest speaker.’’

The White House did not respond to a request for comment.

Some took to Twitter to voice their criticism.

"Companies, be advised: if you encourage your employees and/or contractors to attend the political rallies of a man who separates children from their families, you will be placed on the #GrabYourWallet boycott list,'' Shannon Coulter, who launched the GrayYourWallet campaign, said on Twitter Monday.

But some supported the event.

"The plant was closed the day the President went there,'' read one tweet in response to the threatened Shell boycott. "Employees could attend, use PTO for the day or take without pay. Very generous on part of the employer. Trump 2020!!!!"

USA TODAY asked legal and workplace experts for their take on the event.

Is it legal to tie a worker's compensation to showing up at a political event?

"No laws were broken by this type of arrangement,'' says Jay Hornack, an attorney and professor at University of Pittsburgh's law school. "If an employer is requiring an employee to report to work and perform certain services, or sit and listen to someone speak... then there’s no restriction on employers saying 'This is what we're going to pay the employee to do during this time.' ''

Employees can be required to attend an event like Trump's speech in Pennsylvania because, "It is, in fact, legal for employers to hold rallies of the kind that Shell held for President Trump, and to require their employees to attend and that’s a result of the Citizens United Supreme Court decision, as well as the decision of the Federal Election Commission not to take further action in some earlier cases of employer coercion,'' says Alexander Hertel-Fernandez, assistant professor of international and public affairs at Columbia University and author of “Politics at Work’’

The high court lifted limits on independent spending by corporations and unions in 2010's Citizens United case.

Is it ethical for employers to ask their employees to participate in such an event?

"Ethically it’s a much more difficult question,'' says Hornack. "Arguably this situation is one where they ... took away or limited free choice on the part of the workers. That they felt like they really had no choice, because of the money, than to go to the event.''

Hertel-Fernandez agreed. “I think it’s unethical because employers have a really special type of leverage over workers that’s not like the leverage that, say, a political party or a grassroots organization ... might have over you,'' he says, "That’s because employers are ultimately responsible for cutting the checks that form your wages and your health benefits and pension benefits. And that means employees have a hard time saying no.''

Why are employers doing this?

“In the vast majority of cases, companies do think that by helping the business or the sector that they’re in, they’re ultimately helping their employees as well,'' Hertel-Fernandez says. "Just like companies have political action committees and lobbyists, so too is it becoming increasingly standard for companies to think about their employees when they’re making these pushes around elections and legislative debates.’’

It can have an impact on lawmakers. "It's quite compelling for a corporate lobbyist to come in and say 'Hey, I've got 2,000 employees employed in your district who really care about this issue and who are going to vote in the next election.' That’s more compelling than if the corporate lobbyist is just saying we think that this policy should change.''

Is Citizens United the major force behind this shift?

"It actually predates Citizens United,'' Hertel-Fernandez says. "At the turn of the century, it was quite common for employers to be very involved in their employees political lives, sometimes in pretty egregious ways like giving them ballots to use... or even after the spread of secret ballots, marching employees down to the polling booth to make sure that they voted for the right candidate.’’

Employers began to back away from their workers' political lives in the 1950's, but since the 1990's, Hertel-Fernandez says that trend has reversed.

Still, his research has found that "rallies like the one that Shell held are the exception ... when it comes to employer political involvement in the workplace,'' he says. "More common are requests that employees weigh in on legislation that’s pending in Congress or state legislatures. But they still do happen and I think they are a vivid demonstration of the control that employers can exert over their workforce if they’re so inclined. ‘’

Follow Charisse Jones on Twitter @charissejones