Was Israel still under the law in the book of Acts?
Yes. In the book of Acts, Israel is still under the law. When Peter comes on the scene, and even at Acts chapter 8, seven years after Pentecost, the nation remains under the law. Jesus never hinted during His ministry that the Jews were no longer under the law.
Les explains that even in the book of Acts, Israel is still under the law. Peter could see the tribulation, Christ's return, and the kingdom setup coming, so the Great Commission to the ends of the earth was not for Peter and the eleven until they had the king. They were not to go to the ends of the earth under the covenant until they had the king. Les notes that at Acts chapter 8, seven years after Pentecost, Israel is still under the law. During Jesus' three-year ministry on covenant ground, everything He spoke was to the Jew under the law, and He never hinted that the Jews were no longer under the law.