Plaid Cymru Dwyfor Meirionydd MP Liz Saville Roberts said: "The UK government is able to mobilise the army, yet devolved governments cannot mobilise the army... except in extreme circumstances."
Ms Roberts urged UK ministers to "revisit" the issue.
She was speaking during a Commons debate on flooding.
The Welsh government should have the power to mobilise the army to help with floods, an MP has said.