A Conservative Welsh Government would not "tread on Westminster's turf", the party's Senedd group leader has said.
Paul Davies said he would "respect what is not devolved" by "unpicking" the Welsh Government's international relations department, if his party wins power at next year's Senedd election.
Conservative Welsh ministers would also reject recommendations that criminal justice should be devolved, he said.
He was writing for the Gwydir website, before the virtual Tory conference.
Party conferences are being held online this year due to the Covid-19 pandemic.
Mr Davies said he would conduct "a root and branch examination of where Labour has been pretending it has devolved competence when it does not", if successful in next May's election.
He wrote that the international relations brief and the Welsh Government-appointed criminal justice commission were "the real signs of disrespecting devolution".
"If the Welsh Labour government had only focused on the things it had legal powers over, then it might not have made such a hash of them. But it simply can't help itself.
"A Welsh Conservative government will focus on respecting devolution, and respecting what is not devolved too."
A party spokesman told BBC Wales elements of the international relations brief which are devolved, such as responsibility for tourism and the Welsh language, would be retained within the cabinet.
Mr Davies also rejects the Welsh Government's claim that the UK government's Internal Market Bill will see it "steal powers" from Cardiff Bay.
"Not a single power will be taken away from Wales," he said.
"When you ask Welsh Government ministers to wipe away the faux tears and list the powers they are losing, they cannot name one power they are losing.
"Because nothing is being taken away from Wales.
"Powers are being taken back from Brussels and vested where they belong - with the UK and Welsh governments."
Mr Davies has already pledged to halve the number of Welsh ministers to seven, freeze civil servant recruitment and not increase the budget of the body which runs the Senedd if he wins power next year.
The Conservatives are currently the biggest opposition group in the Welsh Parliament, with 11 of the 60 Senedd members.
At last year's general election the party won six key seats from Labour in Wales, and took back a seat it had lost to the Liberal Democrats in a by-election, taking its tally of Welsh MPs to 14, the highest since 1983.