Is he refering to continual state of sinning, one time sins, or what?
A person cannot sin while being led of the Spirit. But that Christians can grieve the Spirit and revert back to the flesh is evident in all our lives.
Gal 5:16 This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
17 For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.
It would not have been necessary for Paul to tell us to walk in the Spirit if we could not also revert back to the flesh.
Eph 4:22
That ye put off concerning the former conversation the old man, which is corrupt according to the deceitful lusts;
23 And be renewed in the spirit of your mind;
24
And that ye put on the new man, which after God is created in righteousness and true holiness.25 Wherefore putting away lying, speak every man truth with his neighbour: for we are members one of another.
26 Be ye angry, and sin not: let not the sun go down upon your wrath:
27 Neither give place to the devil.
28 Let him that stole steal no more: but rather let him labour, working with his hands the thing which is good, that he may have to give to him that needeth.
29 Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace unto the hearers.
30 And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.
Just because we have the indwelling Holy Spirit does not mean we cannot sin. Paul tells us to "put off" the old man, and "put on" the new man. So, this is something we must consciously do. Paul tells us not to lie or steal, to earn an honest wage, not let corrupt communication proceed from our mouths... So, putting on the new man and obeying the Spirit is something we have control over in our lives and is expected of us.