Many supporters of Israel are understandably upset with the Boycott, Divestment, Sanctions movement that seeks to encourage governments and businesses to boycott goods and services from Israel in response to perceived human rights or other alleged abuses.

For example, hardly a school year goes by nowadays without various student governments at American colleges voting to have their institutions “divest” shareholdings in companies that do business with Israel. Just last month the same thing happened at the University of Toledo in Ohio.

Supporters of Israel see this movement as unjustified, even immoral. Even setting aside the merits, the efficacy and morality of boycott movements itself is a matter of some debate. Yet whatever you think of the movement or of Israel, the solution is not bad law, no matter how good the intentions.

Last Wednesday,  Reps. Doug Lamborn, R-Colo., and Ron DeSantis, R-Fla., introduced the Boycott Our Enemies, Not Israel Act. The legislation would require any prospective contractor with the U.S. government to certify it is not taking part in any boycott against Israel. Regardless of whether you agree with this policy goal, the law falls afoul of the First Amendment in two glaring ways.

First, it is not clear one can define “boycott” in any way that is not unconstitutionally vague or overbroad. Similar legislation introduced earlier this year defined a boycott as “politically motivated” actions that are “intended to penalize or otherwise limit commercial relations specifically with Israel…”

What is “politically motivated?” Say you are a company that does business in Israel (Google, for example) and you get wind of data theft. If you attempt to lobby the Israeli government or the U.S. government to help you and threaten to cease doing business in Israel if you do not get your way, this certainly falls within the four corners of the legislation. But it seems like core expressive conduct protected by the First Amendment. A reasonable government contractor will face many situations like this and will have no idea what expression is permissible, and what is not. This is a classic case of vagueness that offends the First Amendment.

A second important way the legislation violates the First Amendment is that it clearly runs afoul of a recent Supreme Court decision, Agency for International Development v. Alliance for Open Society International. That case involved a U.S. Agency for International Development anti-AIDS program that required all recipients of program funds to affirmatively state they opposed prostitution. Even though it seems clear requiring this affirmative statement advanced the anti-AIDS purpose of the program, the Supreme Court held the requirement was actually leveraging funding to regulate speech outside the contours of the federal program itself.

Generally speaking, as outlined in a 1991 Supreme Court case, Rust v. Sullivan, Congress can impose limits on the use of funds it hands out. But, as Agency for International Development v. Alliance for Open Society International makes clear, Congress cannot “go beyond defining the limits of the federally funded program to defining the recipient … our ‘unconstitutional conditions’ cases involve situations in which the Government has placed a condition on the recipient of the subsidy rather than on a particular program or service, thus effectively prohibiting the recipient from engaging in the protected conduct outside the scope of the federally funded program.”

Prohibiting U.S. government contractors from engaging in anti-Israel speech hardly seems germane even to laws relating to U.S.–Israel trade, let alone laws that are purely domestic in nature. Why should a group that receives federal funds for a soup kitchen, for example, be prohibited from joining the divestiture movement? The anti-speech condition in no way would facilitate better distribution of soup.

So what can congressional opponents of the movement do? Specifically, they can pass legislation prohibiting the use of federal funds to espouse its message, provided the law is clear enough. Such a prohibition would allow organizations to continue to exercise their First Amendment rights to criticize the state of Israel without allowing federal funds to subsidize that speech, thus avoiding constitutional problems.