From the article:
“...It does not matter if the City Government, State Government or Federal Government issues such an edict. Said entities can require that as a condition of all new agreements but they cannot retroactively change the agreements that exist.”
In an existing contract, any changes must go through negotiation; a contract mod is then put in place.
The point here is the same as noted in the article, it must be a negotiation.
Mandates are not negotiations.
Cancelled Mandalorian actress, Gina Carano, sticks to her conservative principles on her movie project and rejects mandates:
Fauci, HHS Officials Discuss Using New Virus From China To Enforce Universal Vaccines In Footage From Oct. 2019
https://gab.com/Dagny_Taggart/posts/107113199052306573