Limiting WAN access

I have setup a test link between two nodes in my basement and as an experiment was able to provide access to the web via one of the node's WAN ports on a Microtik ac HAP lite.  My concern is that if I set this up on the mesh then perhaps it presents an open WAN channel to all nodes which could be an issue regulatory and bandwidth wise.

Is there a way to limit such a WAN gateway so that only a specific remote node can use the feature?

Thx Adrian VE7NZ