We present radial velocity measurements of four wide halo binary candidates from the sample in Chaname & Gould ( 2004 ; CG04 ) which , to date , is the only sample containing a large number of such candidates .
The four candidates that we have observed have projected separations > 0.1 pc , and include the two widest binaries from the sample , with separations of 0.45 and 1.1 pc .
We confirm that three of the four CG04 candidates are genuine , including the one with the largest separation .
The fourth candidate , however , is spurious at the 5-sigma level .
In the light of these measurements we re-examine the implications for MACHO models of the Galactic halo .
Our analysis casts doubt on what MACHO constraints can be drawn from the existing sample of wide halo binaries .