Obey the Law unless that causes us to dis-obey God.

Was God telling Moses to be deceptive to pharoah by saying they were going to sacrifice instead of saying they were leaving.  Was God telling Samuel to be deceptive when he went to annoint David and let Saul think he was just going to sacrifice ?

They did go and sacrifice but they also did the hidden agenda.   Moses and Samuel also knew more of God's plan beyond Moses' and Samuel's involvement in it.  Moses and Samuel told the truth but they did not share everything they knew with the king.   They were being loyal to God but dis-loyal to the Kings.
Is it Okay with God for us to decieve the government?  Is there a difference between lies by commission and lies by ommision?    What about people who sneak Bibles into certain countries and share the gospel there.  At what point do we violate our nations laws that we disagree with because of our Christian world view?

God told Moses that God will bring His people up out of Egypt and into the promissed land (Exodus 3:8)
He told Moses "you may bring my people out of Eqypt" (Exodus 3:0).  Notice that He did not tell Moses that Moses would bring the people into the promised land.

Say to the king of Egypt "let us go three days into the wilderness so that we may sacrifice to the Lord our God" (Ex 3:18)

Moses and Aaron say "God says 'Let my people go that they may celebrate a feast to me in the wilderness'" (Ex 5:1)  "Let us go 3 days journey into the wilderness tha twe may sacrifice to the Lord our God" (Ex 5:3)

Then they set out and camped on the edge of the wilderness (Ex 13:20).  They went 3 days into the wilderness (Ex 15:20)   The people grumbled for lack of  good water (Ex 15:24),  God made the water sweet (Ex15:25).  They came to a place with 12 springs and 70 date palms (Ex 15:27).  They set out again (Ex 16:1) they grumbled about lack of bread and meat. (ex 16:2-3).  God gave them qauils and manna (Ex 16).  God commanded them to take a sabboth rest every 7th day (Ex 16:29).

God sent Samuel to annoint David as King.  Samuel was afraid of what Saul would do if he knew.  God told Samuel "Take a heifer with you and say "I have come to sacrifice to the Lord"   Samuel did as the Lord said.  He Annointed David  before they ate the sacrificed heifer (1 Samuel 16)