Bloomberg reports that the ECB said it will start overseeing “systemic” investment firms as a long-planned legal change adds to responsibilities that have steadily expanded in recent years.

The central bank said in a statement that firms with more than 30 billion euros of assets that underwrite or trade financial instruments on their own account will now have to apply for banking licenses under new legislation that takes effect this week.

European authorities are putting securities firms on a tighter leash to ensure that risks in trading businesses are supervised appropriately. The ECB has steadily expanded its remit since taking on supervision of euro area banks at the end of 2014 and again when international banks started moving operations to the bloc because of Brexit.

A first group will probably enter ECB oversight in the second half of the year, the ECB said.