Probably ARE ... dunno about Construction Materials, but most states have a tax on “Items purchased out of State”. My Comradeship (state) has a whole form for it .. sales tax for catalog and internet purchases.
They’ll find a way to send out a form of Gestapo to enforce it, now that they’re not getting as much revenue,
Try buying the stuff and not telling anyone.
Seems easy enough.
Money orders and gift cards.
You know there is a reason we ship raw logs from BC to the USA right?
Finished lumber get a bill slapped on it... raw logs don’t...