▁" non - pos itive ▁law ," ▁applies ▁to ▁only ▁certain ▁groups , ▁and ▁arg ues ▁that ▁the ▁only ▁types ▁of ▁income ▁sus cept ible ▁to ▁tax ation ▁are ▁" the ▁domestic ▁income ▁of ▁foreign ers , ▁certain ▁foreign ▁income ▁of ▁Americans , ▁income ▁of ▁certain ▁poss essions ▁corpor ations , ▁and ▁income ▁of ▁international ▁and ▁foreign ▁sales ▁corpor ations " ▁He ▁has ▁also ▁c ited ▁the ▁Supreme ▁Court ▁decision ▁Br ush ab er ▁v . ▁Union ▁Pacific ▁Rail road , ▁in ▁which ▁the ▁Court ▁indicated ▁that ▁the ▁Six teenth ▁Am end ment ▁of ▁the ▁U . S . ▁Constitution ▁did ▁not ▁give ▁Congress ▁any ▁power ▁that ▁it ▁did ▁not ▁have ▁already . ▁He ▁also ▁arg ues ▁that ▁the ▁Six teenth ▁Am end ment ▁was ▁not ▁properly ▁rat ified , ▁cit ing ▁the ▁two - volume ▁work ▁The ▁Law ▁that ▁Never ▁Was , ▁co - author ed ▁by ▁William ▁J . ▁B enson . ▁ ▁One ▁of ▁his ▁key ▁statements ▁on ▁income ▁tax ▁is ▁that ▁the ▁United ▁States ▁grew ▁to ▁be ▁the ▁most ▁powerful ▁nation ▁in ▁the ▁Un iverse ▁without ▁requiring ▁such ▁a ▁tax , ▁and ▁that ▁it ▁began ▁to ▁fal ter ▁when ▁the ▁government ▁began ▁to ▁interven e ▁in ▁the ▁economy ▁and ▁individuals ' ▁lives . ▁In ▁the ▁past , ▁he ▁has ▁stated ▁that ▁ref using ▁to ▁file ▁a ▁tax ▁return ▁is ▁just ifiable ▁until ▁the ▁In ternal ▁Re venue ▁Service ▁( IR S ) ▁provides ▁a ▁legal ▁reason ▁for ▁doing ▁so ▁( see ▁Federal ▁stat utes ▁impos ing ▁oblig ations ▁to