It constitutes "matter not committed to them by either House" and makes their conference report subject to a point of order on both the House and Senate floor. Senate Rule XLIV, Paragraph 8: New Directed Spending Provisions

Paragraph 8 of Senate Rule XLIV places an additional restriction on the content of conference reports. The conferees might agree to include in the conference report funding for several similar projects that were not listed in the House bill or in the Senate substitute. Under Rule XXVIII, the provision including funding for additional projects would likely be considered to be reasonably related to the matter sent to conference and therefore not subject to a point of order. Disposing of the Point of Order

The procedure for disposing of a Rule XXVIII or a Rule XLIV point of order allows the Senate to strike "new matter" or "new directed spending provisions" from the conference report but agree to the rest of the terms of the compromise. Because it is not in order for either chamber to alter the text of a conference report, the rule creates a process that converts the text of the conference compromise minus the "new matter" or "new directed spending provisions" into an amendment between the houses. If the Senate agrees to this amendment, it is then sent to the House for consideration in that chamber. Under the process, a Senator can make a point of order against one or more provisions of a conference report. If a point of order is raised against more than one provision, the presiding officer can make separate decisions regarding each provision. The points of order under Rule XXVIII and Paragraph 8 of Rule XLIV can be waived with the support of three-fifths of all Senators duly chosen and sworn (60 Senators if there are no vacancies).
Two Senate rules affect the authority of conferees to include in their report matter that was not passed by the House or Senate before the conference committee was appointed. Colloquially, such provisions are sometimes said to have been "airdropped" into the conference report. First, Rule XXVIII precludes conference agreements from including policy provisions that were not sufficiently related to either the House or the Senate version of the legislation sent to conference. Such provisions are considered to be "out of scope" under long-standing Senate rules and precedents. Second, Paragraph 8 of Rule XLIV establishes a point of order that can be raised against "new directed spending provisions," or provisions in a conference report that provide specific items of appropriations or direct spending that were not committed to the conference committee in either the House or Senate versions of the legislation. Both of these restrictions can be enforced on the Senate floor if any Senator chooses to raise a point of order against one or more provisions in a conference report.
The process for disposing of either a Rule XXVIII or a Rule XLIV point of order allows the Senate to strike "out of scope matter" or "new directed spending provisions" from the conference report but agree to the rest of the terms of the compromise. It is not in order, however, for either chamber to alter the text of a conference report, and therefore the process converts the text of the conference compromise minus the "new matter" or "new directed spending provisions" into an amendment. If the Senate agrees to this amendment, it is then sent to the House for consideration in that chamber. The points of order under Rule XXVIII and Paragraph 8 of Rule XLIV can be waived with the support of three-fifths of all Senators duly chosen and sworn (60 Senators if there is no more than one vacancy). A figure at the end of the report outlines the procedural steps for disposing of these points of order when they are raised against conference reports.