1.   It is almost impossible to amend the bill and remove the provision at this late stage, lawmakers say.

2.   The bill was amended several times during its passage through Congress.

3.   As the negotiations on a compromise proceeded in private, Republicans tried but failed on the Senate floor to amend the bill in a significant way.

4.   Barr also said that he intends to research whether he can amend the spending bill that funds HUD to prevent the agency from filing a lawsuit against gun makers.

5.   Backers of the amendment scoffed at fears that amending the bill would doom the larger bill this year.

6.   Aides to Shelby said he would like to see the bill amended so that potential targets of the law would have strong protections.

7.   But amending bills requires staff time and costs money for printing.

8.   But before the House can begin to create an acceptable bill, members need the freedom to amend the bills that their leaders will put before them.

9.   But they have no assurance that they will prevail because it is unclear how their bill might be amended in debate.

10.   By Thursday afternoon, the Senate voted unanimously to amend the bill.