According to Parashara Smriti (PS), during "ApatkAla" or during an emergency, following/maintaining Dharma must take a backseat. Preserving one's life, at that time, is the only priority. And, one should wait for the unrest to be over.
So, this is in other words the same as saying "One can abandon the Dharma ShAstras temporarily till the emergency is over".
Deshabhange pravAse vA bhyAdhishu vyasaneshvapi |
RanedevasvadehAdi paschAddharmam samAchAret ||
- During a civil commotion, or in exile, or when ill, or in misfortune, the first consideration is to preserve one's life ;
practice of religion should at the time be postponed.
So, the king can very well use this injunction to issue such an order that abandon following the ShAstras till the unrest is over. But, I do not know of any such explicit verse where a king is specifically instructed to do so.
The above verse is PS 7.35. The next two verses are as follows:
- By any kind of conduct, soft or cruel, one should deliver himself from a distressed state ; the practice of religious rites ought to be
left for a period when he is equal to the task.
ApatkAle tu nistirno sauchAchAram tu chintayet |
samuddharet pashchAtswastho dharmam samacharet ||
- After the misfortune is over, one should think of purification and religious rites. Thereafter purity may be recovered by him. He ought
to practice religion when his troubles are past.
Regarding your question about curfew, I have no idea.