According to Ranhillo Aquino-Callangan, Dean of the San Beda Graduate School of Law, in a Facebook post...
A STATE OF LAWLESSNESS
Nothing alarming, but neither is it legally insignificant.
1. It is a declaration by the Chief Executive that there is notable lawlessness in the country.
2. It lays down the premise for the exercise of the "calling out" power: Article VII of the Constitution allows him to call out the armed forces to suppress "lawless violence". The result is that law-enforcement is not left only to the police but is entrusted to the Armed Forces who will assist the police in quelling mayhem.
3. It is a signal to the Legislature that he may ask for emergency powers.
Are checkpoints allowed? Even without a declaration of a state of lawlessness, they are allowed. Only that their usefulness becomes more urgent now. Does that allow police officers to search so thoroughly that they can forcibly open gloves and baggage compartment? No, but they can request you to open these and it would be wise for one to cooperate.