IT weights can be changed at anytime

[jjjanos]

We all know that the IT-section of the GCR says..

At the end of a vehicle’s fourth year of Improved Touring classification, an assessment of class equity shall be made and the vehicle’s minimum weight shall be established.

Which would seem to say that at the end of the 4th year, the weight of the car is set in stone... but that's not true.
First - Sporting regulation 1.2.2.A clearly says...

The SCCA may revise, in its sole discretion, the GCR or issue Supplements to it, at any time through “FasTrack,” “Racing Bulletins,” or “Tech Bulletins”, or on the official SCCA website. All supplements will have a published stated date.

That's pretty damn clear - SCCA can revise ANYTHING in the GCR and such revisions, by definition, cannot be in violation of ANY section of the GCR.
Second - The GCR is not the ultimate source of authority in SCCA. In the U.S., the power/authority of the legislative branch (The CRB/BOD) are constrained by what Constitution (the GCR) grants that body. In SCCA, the power/authority of the GCR (Constitution) is constrained by what the BOD[CRB] grants the GCR.
The GCR doesn't even define the rules underwhich SCCA holds club racing events. Sport regulations 3.5.1 trumps the GCR (!)

Before a sanction can be issued, the Club Racing Board must approve all Regulations different than those of the GCR.

If the Supplemental Regulations say X and the GCR says not X... the event allows X because the Supplemental Regulations are CRB-approved, one-event only alterations to the GCR.

[John Nesbitt]

The GCR doesn't even define the rules underwhich SCCA holds club racing events. Sport regulations 3.5.1 trumps the GCR (!)

Before a sanction can be issued, the Club Racing Board must approve all Regulations different than those of the GCR.

If the Supplemental Regulations say X and the GCR says not X... the event allows X because the Supplemental Regulations are CRB-approved, one-event only alterations to the GCR.

As a practical matter, the approval process for supplemental regulations (Executive Stewards and CRB ) will approve supps which supplement the GCR, but not override the GCR.

For example, an event's supps could specify a blend line at pit out, and penalties for crossing it. Or they could specify certain regional-only classes. These would be supplements to the GCR rules for that one event.

However, and also for example, supps which took away a competitor's right to protest would not pass the approval process since they override the GCR.