I remember Lupin saying, when transporting Harry in Harry Potter and the Order of the Phoenix:
"Brooms," said Lupin. "Only way. You're too young to Apparate, they'll be watching the Floo Network and it's more than our life's worth to set up an unauthorised Portkey."
Harry Potter and the Order of the Phoenix, chapter three, "The Advance Guard"
But later on, when Dumbledore transfers Harry and the Weasleys to Grimmauld Place:
Dumbledore was now rummaging in a cupboard behind Harry and Ron. He emerged from it carrying a blackened old kettle, which he placed carefully upon his desk. He raised his wand and murmured "Portus"; for a moment the kettle trembled, glowing with an odd blue light, then it quivered to a rest, as solidly black as ever.
Harry Potter and the Order of the Phoenix, chapter twenty-two, "St Mungo's Hospital for Magical Maladies and Injuries"
My question is why can't the Order set an unauthorized Portkey if Dumbledore does it so valiantly?