Democrats renewed their symbolic effort to end state right-to-work laws Wednesday, reintroducing legislation to rewrite the federal labor law to prohibit states from having them.

The legislation is unlikely to be taken up in the Republican-controlled Congress.

Right-to-work laws prohibit private-sector workers from being forced to join or otherwise financially support a union as a condition of employment. The laws have experienced a surge in popularity in recent years, with six states adopting them since 2012, bringing the total number to 27. Unions hate the laws, which are associated with declining membership and depleted treasuries as workers opt out of membership.

The union's Democratic allies argue that weakening unions is really a covert attack on workers. "The Workplace Democracy Act restores real bargaining rights to workers and repeals the right-to-work laws like those that [Wisconsin Gov. Scott] Walker has used to undercut American workers," said Rep. Mark Pocan, D-Wis., a co-author of the legislation with Sen. Bernie Sanders, I-Vt.

Proponents of the laws argue Democrats are serving the interests of union leaders, not rank-and-file workers. "Alternate headline: Democrat senators introduce bill to force tens of millions of American workers to be fired if they don't fund unions that are some of the largest donors to Democrats," tweeted the National Right to Work Legal Defense Foundation.

Pocan and Sanders' legislation would rewrite the National Labor Relations Act to void the state laws. It also would effectively end federally monitored secret ballot workplace elections in union organizing drives. Instead, it would allow unions to be recognized if a majority of workers sign cards saying they want one, a method dubbed "card check." Unions argue that would end union-busting campaigns by employers, but critics say it would allow unions to manipulate the process.