Jewish rabbis agree that praying for the dead is necromancy

There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch,

Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer.

ALIBI: In fact, he has not, because he at times has given it—for example, when he had Moses and Elijah appear with Christ to the disciples on the Mount of Transfiguration (Matt. 17:3).

RIGHT ANSWER: This is a vision from God.
 
Matthew 17:9 "And as they came down from the mountain, Jesus charged them, saying, Tell the vision to no man, until the Son of man be risen again from the dead."

Besides why do you ask Lord Jesus Christ to follow the commandment in Deuteronomy 18:10-11?

The commandments of God are for people who do sin.

1 Timothy 1:9 Knowing this, that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and for sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers,  

1 Timothy 1:10 For whoremongers, for them that defile themselves with mankind, for menstealers, for liars, for perjured persons, and if there be any other thing that is contrary to sound doctrine;

Jesus is sinless (1 Peter 2:22) and a true God (1 John 5:20) so you should not ask Him to follow the commandment in Deuteronomy.

We people are obliged to follow what God had commanded us to do. To follow his Laws.

Ecclesiastes 12:13 Let us hear the conclusion of the whole matter: Fear God, and keep his commandments: for this is the whole duty of man.
And one of this is not to consult the dead including praying to some of them.