According to John Calvin, everything is under God’s control and authority, according to the will of God. By His authority Satan is curbed by His bridle. If God curbs Satan by His bridle, why did He allow him to tempt and bring evil to the world? If God works everything according to the counsel of His will, then where does free will of human beings stand?
You have just posed questions that have been asked through the centuries. Let’s start by answering the question: Do God’s creatures (angels and mankind) have a free will? YES, they do. Long before God created man, God’s most powerful angel (Lucifer), who was full of beauty and wisdom, exercised his free will and rebelled against God. I would encourage you to read Isaiah 14:12-14 and Ezekiel 28:12-15. In Ezekiel you will read of how God created him in PERFECTION “till iniquity was found in him.” In Isaiah you will read of how Lucifer said in his heart, “I WILL ascend into heaven, I WILL exalt my throne above the stars of God; I WILL also sit on the mount of the congregation on the farthest sides of the north; I WILL ascend above the heights of the clouds, I WILL be like the Most High” (14:13-14). No one can read this and then teach that Lucifer didn’t have a FREE WILL. We know from other scriptures that many angels followed Lucifer (who became the Devil and Satan) in his rebellion and they too exercised their free will.
When God created Adam and placed him in the garden of Eden, He gave him a commandment and the choice to obey it or disobey it. Adam made the wrong choice by disobeying God (see Genesis 2:15-17 & 3:6 with Romans 5:12). No one can say that Adam (and his wife) didn’t have a free will, for “a choice” implies that one has a will. God chose to create the angels and man with this “freedom of choice.” Perhaps He could have chosen to “create robotic creatures” and program them to obey, but “according to the counsel of His will” He chose to give them a free will and let them decide to obey or disobey, to submit or to rebel. Didn’t God KNOW that Lucifer and other angels would exercise their free will and choose to rebel against Him? And didn’t God KNOW that Adam and his wife would exercise their free will and choose to disobey Him? He surely did, for one of God’s Divine attributes is OMNISCIENCE, which means He is “all-knowing” (see Psalm 139:1-6).
Your next question is all-important, “Why did God allow Satan to tempt man and bring evil to the world.” We could also ask, “Why did God allow Lucifer to rebel against Him which brought evil into the universe? Let me say this, and I don’t mean to sound “simplistic”: God would never have allowed sin to come in if He didn’t have a PURPOSE in allowing it to happen. As we already saw, God gave them a FREE WILL so they could “choose to love and obey Him,” all the while knowing they would make a fatal choice. Scripture teaches us that God allowed these rebellions against Him for a REASON; in fact, He has a DOUBLE PURPOSE, to bring 1) glory to God, and 2) blessings to man.
With Satan, God is now USING HIM TO TEST BELIEVERS so they can learn valuable lessons and grow spiritually. I would encourage you to read Job 1:6-19 where Satan was “allowed to test Job” to see if his faith would falter or become stronger. After Satan took all of Job’s possessions and his children away, Job PASSED THE TEST! We read in verses 20-21, “Then Job arose, tore his robe, and shaved his head; and he fell to the ground and WORSHIPED. And he said: ‘Naked I came from my mother’s womb, and naked shall I return there. The LORD gave, and the LORD has taken away; blessed be the name of the LORD.” Satan was but a tool in God’s hand which led to “God being glorified” and “Job’s faith being confirmed and strengthened.”
With mankind, God allowed them to exercise their free will and sin so He could show them His LOVE AND GRACE in providing a Savior. The most well-known verse in the New Testament says, “For God SO LOVED THE WORLD that He gave His only begotten Son, that whosoever believes in Him shall not perish, but have everlasting life” (John 3:16). Man’s free will and their sin gave God the opportunity to REVEAL to lost sinners His heart of love and willingness to “not spare His own Son, but delivered Him up for us all” (Romans 8:32). It was God’s will that His Son go to the cross to pay man’s debt of sin and the one who receives His Son by faith becomes a child of God (John 1:12-13). What did Adam know, before he sinned, of God’s love and grace and His willingness to forgive sinners at such a cost to He and His Son? Adam knew nothing of this. He knew God was a benevolent Creator who provided him with food, shelter, good health, and a good wife, so he knew God was GOOD, but he could not know of God’s infinite love till sin came in through an act of his own free will. In providing a Savior “God was glorified” and “man was blessed with salvation.” I could add other ways in which “God has been glorified and man has been blessed.” They all are due to the fact that “God gave man a free will and He allowed them to exercise their free will and sin.” (DO) (605.5)