You typically need to notify other members of a treaty of your withdrawal, and then there's some time delay until you're no longer bound by the terms. You can't just secretly withdraw, or treaties wouldn't be very meaningful.

EDIT: Yeah. The submitted article says that it happens in six months from today, and here's the treaty text on withdrawal:

https://www.un.org/en/genocideprevention/documents/atrocity-crimes/Doc.44_convention%20antipersonnel%20mines.pdf

Article 20

Duration and withdrawal

1. This Convention shall be of unlimited duration.

2. Each State Party shall, in exercising its national sovereignty, have the right to withdraw from this Convention. It shall give notice of such withdrawal to all other States Parties, to the Depositary and to the United Nations Security Council. Such instrument of withdrawal shall include a full explanation of the reasons motivating this withdrawal.

3. Such withdrawal shall only take effect six months after the receipt of the instrument of withdrawal by the Depositary. If, however, on the expiry of that six- month period, the withdrawing State Party is engaged in an armed conflict, the withdrawal shall not take effect before the end of the armed conflict.

4. The withdrawal of a State Party from this Convention shall not in any way affect the duty of States to continue fulfilling the obligations assumed under any relevant rules of international law.