Deductions & credits

According to Andersen LLC, the Washington state capital gains excise tax may be used to offset federal capital gains.

 

https://andersen.com/uploads/white-papers/Federal_Tax_Implications_of_Washington_State’s_New_Capital_Gains_Excise_Tax_-_No_Contact.pdf

 

Does anyone else have an opinion on the legality of this opinion?

 

Edit: to use the link, make sure you highlight the WHOLE link (not just the blue highlighted part)