Which Mexican law or regulation restricts entry from the US to Mexico via the land border?

Traveling from Mexico to the US is restricted by this notification issued by the DHS and continually extended every month. However I can't seem to find an exact law restriction land border travel to Mexico from the US. The Mexican consulate in the US merely re-iterates the US version of the restriction, even if you switch to the Spanish version of their website. Every other website that I can find likewise merely refers to the US regulations, not the Mexican regulations. I can also find news of the Mexican state of Sonora closing the border in July 2020 but this seems like a temporary regulation that only applied to one state.

Hence... does this law or regulation actually exist on the Mexican side? In practice the land border is definitely open but I prefer to follow all rules and regulations, so I won't be driving into Mexico unless I'm certain that its legal to do so. Going back to the US won't be a problem as I fall under one of the exceptions so I just need to make sure I won't be in violation of any Mexican regulations.