Two House Democrats on Monday called on their colleagues to reject a bill on the floor Tuesday aimed at giving people the right to "unlock" their cell phones and use them with different phone service carriers.

The bill in question is the Unlocking Consumer Choice and Wireless Competition Act, H.R. 1123. The bill as passed out of the House Judiciary Committee was broadly supported by both parties, and was headed toward an easy suspension vote this week.

Specifically, it would broaden an exemption to let people use their phones with other carriers, a change supported by consumer groups, both parties and the Obama administration.

But the version of the bill the House will consider contains additional language not considered by the committee. That language would exempt "bulk unlockers" from the bill.

That means companies could not go into the business of reworking phones so they can be used with other carries, and then reselling them. In a letter to other House colleagues today, Reps. Zoe Lofgren (D-Calif.) and Anna Eshoo (D-Calif.) said this change unnecessary restricts the bill, and that it should be voted down.

"Congress should work to roll back abusive practices that use copyright law to prevent owners from having control over the devices they lawfully own," they wrote. "What it means to 'own' a device that has been purchased is what's at stake here."

The members said exempting bulk unlockers goes against a recent court decision that many see as giving a green light to activities similar to bulk unlocking.

The two members also criticized the way GOP leaders changed the bill without letting anyone know until the new version was posted.

"It is sad that the bipartisan consensus reached during mark-up in the Judiciary committee to improve the law has been destroyed by a secret decision of the majority after the bill was reported out," they wrote. "We urge a no vote on the Unlocking Consumer Choice Act… so that, in the future, we can develop consensus for legislation that provides real protection for consumers, promotes competition, and unlocks innovation."

The Democrats noted that two groups who had supported the bill, Electronic Frontier Foundation and Public Knowledge, withdrew their support for the bill after the changed version was released.

It's not immediately clear whether the opposition from Lofgren and Eshoo will be enough to stop the bill. House Republicans are calling it up under suspension, which means just a two-thirds majority vote is needed.

Assuming every Republican votes for the bill, they'll need about 55 Democratic votes to pass the bill with this super-majority.