That tax will only effect residents purchasing in the state of PA. Out of state taxes (Sales tax and tobacco tax), still do not have to be collected at the time of purchase, so anyone purchasing in the other 49 states WILL NOT be required to pay tobacco taxes at the time of purchase if there is a tobacco tax imposed in PA. They currently don't collect sales tax now either on out of state purchases.
Same as it was before, the purchaser is responsible for paying their state tobacco and sales taxes on online purchases from out of state vendors when they file their taxes if they were not collected at the time of purchase.
A few years back, a member here in CO bought cigars online from a shop in OH and a year later got a letter from CO saying he owed CO taxes for that purchase, not OH.
I imagine at some point there will be taxes collected for each state on all online purchases at the time of purchase, but that is a different conversation....
If you are a PA resident then you should definitely let your voice be heard, a 40% tax is ridiculous right out of the gate.